I have a model with a couple hundred animations (actions), and I just decided to add a new bone constraint for a couple bones, for the purpose of IK-targeting a couple limbs to a prop for a new animation (the hands need to be locked to handlebars on a bike riding animation.)

So, I added a "copy location" constraint to target my arm controller to this object. It works beautifully. I keyframed the "influence" value to 1 for the entirety of the actions where I want these limbs to be constrained.

My dilemma is: Now I have a couple hundred animations in this same file that don't have keys on this bone constraint influence value, and so if I happen to select one of these new animations, that influence value "carries over" to whatever action I select next. This is also an issue when exporting to FBX.

So my question is: Is there a way to efficiently do something like insert default keys on all of my actions at frame 0, so my other actions remain as they were before?

Or alternatively, is there a way to tell blender to use a ref pose value for this influence if there aren't any keys set?

This is an issue I run into time and again, every time I need to add a new bone or constraint to my rig, so I hope there's some workable solution here that doesn't involve manually selecting every action I've animated so far and inserting keys at time 0.